If you knew Islam, read Quran, and believed on Allah, you would not have written what you wrote. Because real punishment in Islam is not punishment in this life but punishment after death, and if a person is really guilty of blasphemy or any crime (Zina, or whatever), even if such guilty gets away in this world his punishment would be there after death.
When Islam punishes someone of crime, that punishment is not to harm or hurt someone, but for only two reasons. One is to stop people harming, cheating, abusing and accusing innocent other people (punishment for crime against other humans) and to stop spreading of immorality in society (ex: Zina in public, that is Zina where enough people seen the Zina and chances is that if not punished than Zina would spread). Islam never promotes ‘tajasus’ (looking intentionally) for guilty in Muslims but it promotes covering, such that, one believe of Islam is that, if a person do a sin (or crime) then covering it up and feeling guilty about it itself is atonement.
So, more important for Muslim is not to punish culprits but save innocent and punish those who are guilty of punishing innocents. In such process, if guilty, especially guilty whose guilt has not physically or materially harmed anyone, gets away so be it.
As for Blasphemy is concerned, this is such sin that one have to think 100 times before punishing even confirmed culprit, because sin or wrong is against Allah (the most merciful) or Prophet (Mercy for all) and we do not know who Allah and Prophet (SAW) forgive for that wrong against them and when.
Further, victimising or punishing for such sin does not do any favour to the name of Prophet (SAW) or Islam, rather malign and defame Islam as well as name of prophet (SAW) all over the world. Thus victimiser also becomes guilty of Blasphemy with his acts that defame and malign name of Prophet (SAW).
For instance, Prophet (SAW) name is respected and loved by Muslims and that is no big deal. Big deal is that Prophet (SAW) name was/is respected name even amongst non-believers, not because he was Prophet or his mission became a successful mission, but because he (SAW) was most merciful and graceful person who always forgave his ardent opponents, abusers, and enemies. Plus, his message is seen as message of equality, justice and forgiveness. Similarly, Islam was/is respected because of same reason, preaching of equality, justice, and forgiveness.
Now, Jahanumi thugs abusing and victimising innocent or guilty in his (SAW) name and in the name of Islam (certainly a ploy of Shaitan) is defaming, maligning, and demonising name of Prophet (SAW) and Islam amongst non-Muslims and creating anxiety and hate amongst Muslims towards those who are doing all this evil in the name of their beloved prophet (SAW) and religion Islam.